One key way dogs differ from wolves, scientists have discovered, is in their ability to digest starchy foods, indicating that the split between the two species may have come about as dogs adapted to scavenging human leftovers.
Scientists still don't know when and where dogs and their wild ancestors the wolves went separate ways, but it seems to have happened more than 10,000 years ago somewhere in Asia. During this change, the new research shows, dogs went through several developmental steps that adapted their digestive system to a diet richer in starches than that of wolves.
"Strikingly the amylase gene is present in many more copies in the dog genome than in wolves. Amylase carries out the first step of the starch digestion”, says Erik Axelsson of Uppsala University.
"Our results show that it was crucial for the survival of early dogs to be able to live on food that largely consisted of vegetables, such as root vegetables and cereals. This in turn indicates that the domestication of dogs may be connected to the human development of agriculture and that it was on the scrap heaps of early settlements that the first steps of the development of dogs took place."
Interestingly, a similar adaptation to increased intake of starches - though a less extensive one - has also been identified in humans.This, says the team, reflects how tightly linked the evolutionary history of humans and dogs is.
Alongside the clear adaptation of dogs’ digestive system, the researchers also found many differences in genes that affect how the brain is developed. Several of these changes, they say, could show why dogs behave differently to wolves.
"It was exciting to see that half of the domestication signals in the genome point to genes that have to do with brain development and function," says professor Kerstin Lindblad-Toh of SciLifeLab Uppsala.
"This shows how changes in both behaviour and diet have been of importance to dogs as they adapted to a life close to humans."